Abstract To determine time related changes of microbial colonization of burn wounds and body flora of burned patients, a prospective study was carried out. Fifty-one patients who were hospitalized at least 3 weeks were enrolled in the study. Periodic swabs were taken from burn wound, nasal, axillary, inguinal, and umblical regions of the patients on admission and 7th, 14th, and 21st days of hospitalization. The mean body surface area burned was 22.9%. A total of 1098 microbial isolates were detected during the study period. Coagulase-negative staphylococci (CNS, 63.0%) and Staphylococcus aureus (19.7%) were the most prevalent isolates in admission cultures. There was a gradual decrease in the number of isolates of CNS and a marked increase in the numbers of S. aureus and Pseudomonas aeruginosa from admission to 21st day. At the 21st day, the most frequent organisms were S. aureus (37.6%), CNS (34.7%), and P. aeruginosa (16.2%). Methicillin resistance of staphylococci strains were increased constantly in study period. While 35.3% of burn wounds were sterile on admission, microbial colonization reached 86.3% within the first week. Nasal carriage of methicillin resistant S. aureus increased from 3.9% to 62.7% at 21st day. The nature of microbial wound colonization and flora changes should be taken into consideration in empirical antimicrobial therapy of burned patients.